Gearing



1945- J. u. SIGNER EI'AL 2,389,557

GEARING Filed Aug. 25, 1943 2 Sheets-Sheet 1 Nov. 20, 1945. J. u. SIGNERETAL GEARING 2 Sheets-Sheet 2 Filed Aug. 25, 1945 a d Z Patented Nov.20, 1945 assassi GEARING Johan Ulrich Signer, West Hartlepool, and LouisMortimer Douglas, Wallsend-on-Tyne, England, assignors to Richardsons,Westgarth & Company Limited, Wallsend-on-Tyne, England, and The ParsonsMarine Steam Turbine Company Limited, Wallsend-on-Tyne, EnglandApplication August 25, 1943, Serial No. 499,906

In Great BritainAugust 19, 1942 7 Claims.

This invention relates to gearing and more particularly to gearing ofthe type known as double reduction gearing.

The state of the art is wholly or in part represented by British PatentSpecifications Numbered 111,329, 116,531, 117,840, 120,257, 120,203 and146,641.

In the usual type of double reduction gear, each primary pinion drivesthe secondary wheel through a single primary gear and secondar pinion.For example, in Figure 1 and 3 of British Patent No. 116.531 the primarypinion b drives the primary wheel which is mounted on the same shaft asthe secondary pinion e which drives the secondary wheel f.. 7

With the object of reducin the weight and size of the gears,particularly of the large heavy secondary gear wheel, proposals havebeen made in which the primary pinion drives through two primary wheelseach of which is associated with a secondary pinion sothat the powertransmitted 'per secondary pinion is only one half of that transmittedper secondary pinion of the usual desi n.

I With such constructions, in order to ensure that the primary pinion isin proper contact with the teeth of, and drives equally through, eachintermediate shaft and secondary pinion, it is necessary to have a veryexact relative circumferential and longitudinal disposition of the teethof the various interen aging members of the train and in order tomaintain the equality of the drives pinion rigid with each of saidprimary wheels engages a common secondary wheel, said primary drivingpinion preferably having axial freedom relatively to its associatedprimary wheels, and in various more specific features of the same.

Referring to the accompanying diagrammatic drawings:

Figure 1 is a front view of a turbine installation ing an H. P. and L.P. turbine shaft coupled redespite inaccuracies in the gears. it isnecessary to provide means for automatically accommodating suchinaccuracies. V

In British Patent No. 146.641, in addition to permanent adjustment inorder to bring the teeth of both drives into contact initially, the primary pinion shaft is mounted in bearings which are free to move in suchdirection as to permit the primary pinion to move into position to drivethe two primary gears equally.

The object of the present invention is to provide in gearing of theabove described dual secondary drive type improved means forautomatically accommodatin inaccuracies of; the gear teeth. not onlythose inherent in the gear but also those of a transient nature such asmay be caused, for example, by differential thermal expansion.

The invention consists briefly in double reduction gearing of thegeneral characterindicated above wherein a primary driving shaftcarrying two single helical driving pinions with their teeth oppositelyinclined, thus forming a double helical primary driving pinion whichdrives a, pair of single helical primary wheels on separate shaftsindividually engaged each by one of the helical portions of said pinion,and a secondary driving spectively to two primary shafts each carryingtwo single helical primary driving pinions with their teeth oppositelyinclined, each primary single helical pinion driving one of two singlehelical driving wheels b, in on separate shafts. The shafts of these-twoprimary wheels I) b and b1 in. The shafts of these wheels carrysecondary pinions 0 0, c1 c1 engaging a common secondary wheel d. Eachprimary wheel I) b, b1 in is single helical and is driven by one helixonly of the double primary pinion a or m which is double helical.

The secondary gears are preferably double helical as shown but they maybe straight spur or single helical. The double pinions a, a1 have axialfreedom, this being preferably attained by connecting them to theirdriving shafts through couplings which permits relative axial freedom.

- With this construction, if the teeth of the two parts composing thedouble pinions have equal and opposite inclination, the axial forces onthem must be equal, the pinion moving endwise if necessary to maintainaxial equilibrium, and since the tangential forces must be proportionalto the axial force on the teeth the power transmission through each ofthe two drives of each double pinion must be equal.

The secondary gears 0 01 d are disposed axially within the primary gearsa a1 and the secondary wheel 6! is preferably double helical with eachsecondary pinion 0 c1 axially free. lAll the axial forces on a secondarypinion thus balance, and since the primary pinions a or set up axialforces on the secondary pinions c 01, the axial forces on the secondarywheel must be to this extent unequal, with the result that thecircumferential forces are also unequal and more power is transmittedthrough one helix of each of the secondary pinions 0 01 than through theother. In order to make this difference as small as possible, it ispreferred to make the helical angle of the priwheels associated with aprimary pinion may be V disposed axially at the same side of' thesecondary wheels.

An example of such an arrangement is illustrated in Figures 3-5 in whichas regards each pair of primary wheels b b and b1 in, one is disposed infront and the other at the rear of the common secondary wheel d, theturbine being disposed in front and having its H. P. turbine shaftconnected to primary pinion a a and L. P. turbine shaft connected toprimary pinion a1 m.

This arrangement allows the primary wheels of each pair b b and b1 intooverlap one another in axial view and in addition enables the turbinesto be brought close to the secondary wheel d. This is illustrated by areference to Figure 5 in which one of the turbine seats e, packing blockI, turbine cylinder foot g and gearcase h are shown, the dimension :1:indicating the clearance between the turbine cylinder foot and its seatand the nearest part of the gearcase, namely, the keep of the bearingfor the secondary shafts carrying the lower primary wheels b In.

If these primary wheels were disposed between thev turbine and thegearing, the turbine would have to be moved considerably further awayfrom the gearcase in order to avoid fouling and give a reasonableclearance such as :r.

In both the examples described above, the centres of the primary pinionsa a1 and the secondary pinion c or are disposed in the same horizontalplane. This simplifies the construction of the gearcase considerably inthat it permits the portion forming the cover to these elementsincluding wheels b and D1 to have a plane horizontal joint in thisplane, which also contains the joint of the bearings of pinions a m cand 01.

In the above examples the helical angles of the primary and secondarygears are and 45 respectively,v

The invention provides a dual secondary drive with automaticaccommodation not only for any inherent inaccuracies of the gear butalso for those of a transient nature such as may be caused, for example,b differential thermal expansion, and the maintenance of the equality ofthe drives by the foregoing means of axial adjustment permits a simplerconstruction than those in which angular adjustment is employed.

We claim:

1. Double reduction gearing comprising aprimary driving shaft carryingtwo single helical primary driving pinions with their teeth oppositelyinclined, two separate shafts each carrying only a single primary wheelengaged by one of 3. Double reduction gearing as claimed in claim 1, inwhich the secondary pinionsa'nd secondary wheel are double helical andin which the helical angle of the primary pinions and primary wheels ismade small relatively to that of the secondary pinions and secondarywheel to reduce the inequality in the power transmission through thesecondary pinions'to the secondary wheel.

4. Gearing as claimed in claim 1, with a plurality of sets of saidprimary shafts and separate shafts each carrying a primary wheel andsaid secondary pinions acting on the same secondary wheel.

5. Double reduction gearing comprising two primary driving shafts eachcarrying two single helical primary driving pinions with their teethoppositely inclined, four separate shafts each only carrying a singleprimary wheelengaged'by one of the respective single helical drivingpinions,

a secondary driving pinion rigidwith 'each' of said primary wheels, and'a common secondary shaft carrying secon'dary wheel engaging all of saidsecondary pinions, whereby self adjustment and axial equilibrium of saidgearing is provided, said secondary drlving pinions and common secondarywheel being arranged between the helical primary wheels with the primarydriving shafts out of line with the secondary wheels,

and in which the secondary pinions and secondary wheel are doublehelical and the helical angles of the primary pinions and primarywheels" is made small relatively to that of the secondary pinions andcommon secondary wheelto reduce the inequality in the powertransmission'through the secondary pinions to the secondary wheel.

6. Double reduction gearing of the character indicated comprising twoprimary driving shafts each carrying two single helical primaryldrivingpinions, four shafts carrying single helical primary wheels individuallyengaged each by one of the single helical primary driving piniolial. asecondary driving pinion on each of the, four shafts carrying saidprimarywheels and rigid with the primary wheels on said shaft and acommon secondary wheel engaged by all said secondary pinions, saidsecondary driving pinions and common secondary wheel being arranged be-.

tween the helical primary wheels with the primary driving shaft out ofline with the secondary wheel and the centers of all the primary p1n-,ions and one of each pair of the associated secondary pinions beingdisposed in the same plane. 7. Double reduction gearing of the characterindicated comprisingtwo primary driving shafts each carrying two,singlehelical primarydriving pinions, four shafts carrying singlehelical primary wheels individually engaged each by one of the singlehelical primarydriving pinions,,a secondary driving pinion on each oftheshafts carryingsaid primary wheels and rigid with the primary wheels onsaid shaft, and a common sec: ondary wheel engaged by all said secondarypinions, said secondary driving pinions and common secondary wheel beingarranged between the hell: cal primary wheels with the. primary drivingshaft out of line with the secondary wheel and the centers of all theprimary pinions and asso: ciated secondary pinions being above the horizontal center line of the secondary wheel and the centers of all theprimary pinions and one of each pair of the associated secondary pinionsbeing disposed in the same horizontal plane.

JOHAN ULRICH SIGNER. LOUIS MORTIMER DOUGLAS."

